Question for Greg, why did you close the engine noise thread I started earlier ??
Well doesn't matter, here it goes. I'm chasing the origin of the sounds that drives me crazy, I started the bike with the oil cap off, to my dismay, there is a lot of gases that blow trough the the oil cap, I'm curious to see how normal it is for a SH to blow gases almost like an exhaust : pulsing and smelling more like air mixed with oil vapor and exhaust. I just hope it's air moved by the clutch drum sucked trough the crankcase venting system. What I hope it's not, excessive blowby from a fractured ring. The bike don't seem to have lost power, but stall a lot more. It would be nice if someone could tell or try on his bike just so I can move to the next suspect on the list. I'll tear the whole engine apart this winter, but for now I just plan the top end. I'll keep posting and I'll try to post a video of the offending sounds.

Edit : I can answer my own question, I'm just getting paranoid, I'm sure we all become when we chase gremlins. I guess it's the pumping of the pistons when both are coming down.

 

I didn't close the thread. Dunno who did. It's opened again though.

Yeah, that's normal for two big pistons and a small crankcase. That's why we have a breather system connected to the airbox. There is some blowby in all engines, and it occurs the most at high load, high rpm riding. This is normal.